A light train made of two cars travels at 45 mi/h. Car A weighs 18 tons, and car В weighs...

A light train made of two cars travels at 45 mi/h. Car A weighs 18 tons, and car В weighs 13 tons. When the brakes are applied, a constant braking force of 4300 lb is applied to each car. Determine (a) the time required for the train to stop after the brakes are applied, (b) the force in the coupling between the cars while the train is slowing down.